The present disclosure relates to an image forming apparatus, and more particularly to a technique of eliminating static electricity from the surface of a photosensitive body by emitting light thereto.
Image forming apparatuses based on a Xerography method are widely known. The method includes five processes, namely uniformly charging an uncharged photosensitive body (charging process), irradiating the surface of the charged photosensitive body with a laser beam according to a document to be copied thereby forming a latent image of the document (exposure process), visualizing the latent image with a toner (developing process), transferring the visualized toner image onto a sheet (transfer process), and fixing the transferred toner image onto the sheet (fixing process).
In the image forming apparatus that adopts the mentioned process, irregularity of potential before the charging process may create a residual image called ghost, in the formed image. The irregularity of the potential on the surface of the photosensitive body is primarily provoked by a residual charge remaining after the image forming process, and therefore, as a remedy, the static electricity is eliminated from the surface of the photosensitive body, after the transfer process or before the charging process. For example, an illumination unit connected to a light source such as a light emitting diode (LED) is provided so as to oppose the photosensitive body.
Further, in most cases the image forming apparatus includes a plurality of photosensitive bodies, not just one, respectively corresponding to a plurality of colors (for example, black, yellow, cyan, and magenta). Accordingly, the illumination unit has to be provided for each of the photosensitive bodies.
The light source also has to be provided for each of the illumination units. Therefore, when the image forming apparatus includes a plurality of photosensitive bodies, the same number of as light sources and connectors for the respective light sources as that of the photosensitive bodies are required. Thus, a larger space is required for the light sources and the connectors therefor, which is contradictory to the requirement for reduction in size of the apparatus, and the manufacturing cost inevitably becomes higher.
As a solution thereto, for example, a technique of eliminating static electricity from the photosensitive bodies has been proposed that includes employing a single piece of light source, instead of preparing the light source for each of the illumination units.